MyPACS.net: Radiology Teaching Files > Case 868122

previously visited MECONIUM ILEUS
Contributed by: Dr Phillip Silberberg, Children's Hospital Omaha, Radiologist, Omaha Childrens, Creighton University and UNMC, Nebraska, USA.
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Fig. 1: Contrast enema showing microcolon with reflux into distal ileum that is filled with pellets of meconium
Discussion:

 

Meconium ileus is a common cause of distal small bowel obstruction in the neonate.  Meconium will cause no difficulty in a newborn infant if it is eliminated from the bowel within a couple days (1).  It is often an early manifestation of cystic fibrosis (CF). Meconium ileus occurs when inspissated meconium obstructs the small bowel, usually the terminal ileum. About 10-20% of infants with CF present with meconium ileus at birth, but it may be associated more rarely with other conditions such as pancreatic aplasia, pancreatic duct obstruction, or simply decreased intestinal motility with no apparent abnormality (2).  In CF the meconium is thick and viscous, due to the pancreatic enzyme deficiencies and abnormal chloride secretion in the intestine. Clinically, the neonate may have a distended abdomen, failure to pass meconium, and bilious emesis.  

Meconium ileus can be described as simple or complicated. In simple meconium ileus the distal small bowel contains inspissated, thick viscous meconium. The mid ileus is distended up to 7 cm in diameter and the unused colon is small (microcolon) with small amounts of mucus or inspissated meconium. Simple meconium ileus is without complication such as perforation.  Complicated meconium ileus can be associated with volvulus, obstruction, bowel gangrene, perforation, intestinal atresia, pseudocyst formation, or meconium peritonitis (3).  Volvulus occurs due to the distended loops of terminal ileum and can lead to vascular compromise and bowel gangrene. Perforation can occur and cause meconium peritonitis, an inflammatory reaction in the peritoneal cavity. This is generally a sterile, chemical peritonitis and causes irritation of the serous surfaces. With healing, calcifications can take place in variable distributions (1).

 

Imaging

 

            In meconium ileus, plain radiographs show multiple dilated loops of small bowel. The thick meconium has a ground-glass appearance and mixed with air gives the intestinal contents a granular “soap-bubble” sign appearance, usually in the right lower quadrant that is highly associated with meconium ileus (3). The soap-bubble sign may be seen however in Hirschsprung disease, ileal or colonic atresia, or meconium plug syndrome.  Air-fluid levels may be present in the dilated small bowel, but often are not because the meconium is so viscous. In fact the presence of prominent air-fluid levels may be more suggestive of the presence of a complication such as atresia (3).  The diagnosis is confirmed with a contrast enema. Contrast enema will typically show a “microcolon,” which indicates that meconium has not passed naturally through the colon pre-natally. In a properly complete enema, contrast should reflux into the terminal ileum, which is filled with pellets of meconium and establishes the diagnosis (4).  In the absence of contrast reflux into the terminal ileum, surgery may be required to diagnose.

Meconium peritonitis can be incidentally seen on abdominal radiographs due to the formed calcifications (5). Meconium that leaks into the peritoneum secondary to perforation may cause scattered amorphous or curvilinear calcifications (4).  The calcifications generally slowly disappear, but can also be associated with formation of adhesions and subsequent bowel obstruction.

CT and MRI are not indicated in the evaluation of meconium ileus. Ultrasound is used to visualize calcification in meconium peritonitis or provide signs of enlarged bowel loops and distention in utero.

 

Treatment

 

           Therapy can be non-operative or surgical. Non-operative therapy is successful a majority of the time for uncomplicated cases. Contrast enema can be diagnostic and therapeutic.  Dilute water soluble contrast is placed in the colon and advanced into the ileum with fluoroscopic guidance (6). These enemas may be repeated at regular 12-hour intervals until all meconium is evacuated (7).  Success is based on drawing fluid into the bowel and soften the meconium, thus it is important to adequately hydrate the infant. Evaluation for cystic fibrosis is a requirement if the presenting symptom is meconium ileus. Pancreatic enzyme replacement may be required. Other measures specific to treatment of cystic fibrosis may be used.

           Surgery is reserved for those who fail non-operative management. Patients with complications may require surgical intervention as well (8). A variety of surgeries are available including ileostomy with irrigation, resection with ileostomy, and resection followed by anastomosis.  Prognosis depends on the severity of disease and on the progression of cystic fibrosis.

 

 

References:

 

  1. A. Tucker, R. Izant: Problems with Meconium.  Amer Journ of Roent, 1971;112:136-142
  2. MM Ziegler: Meconium ileus. Curr Probl Surg, 1994;31:731
  3. J Leonidas, W. Berdon et al: Meconium ileus and its complications- A reappraisal of plain film roentgen diagnostic criteria. Amer Journ of Roent, 1970;108(3):598-609
  4. W.E. Brant, C.A. Helms: Fundamentals of Diagnostic Radiology, 3rd ed. Lippincott Williams & Wilkins,  Philadelphia, 2007.
  5. A Hekmatnia, et al: Meconium ileus. http://www.emedicine.com/radio/topic427.htm, 2005
  6. G. Doherty, L Way: Current Surgical Diagosis and Treatment, 12th ed. McGraw-Hill Co, Inc, 2006
  7. D. Hackam, K. Newman, H. Ford: Schwartz’s principles of surgery, 8th ed. McGraw-Gill Co, Inc, 2005
  8. J. Fuchs, J. Langer: Long-term outcome after neonatal meconium obstruction. Pediatrics, 1998; 101(4)




Contributed by:
M. Conor Simmons, 4th year medical student, Creighton University, Omaha, NE.
Philip J. Silberberg, M.D., Department of Radiology, Children's Hospital, Omaha, NE
Comments:
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Additional Details:

Case Number: 868122Last Updated: 09-06-2006
Anatomy: Gastrointestinal (GI)   Pathology: Congenital
Modality: GIAccess Level: Readable by all users

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